This invention relates to a bearing structure for an intermediate transmission shaft of the type used in a vessel propulsion and more particularly to an improved arrangement for preloading the thrust bearing associated with a driven bevel gear so as to facilitate adjustment of the gear mesh.
In a variety of applications, a bevel gear train is employed for driving an intermediate shaft. Normally, the intermediate shaft and bevel gear are supported by a thrust bearing arrangement since the bevel gear drive itself creates a thrust on the gear in an axial direction. With such an arrangement, it is necessary to both preload the thrust bearing and to preload the gear so as to adjust its meshing relationship with the driving gear. Obviously, such arrangements require complicated constructions.
In one form of mounting heretofore proposed, it has been the practice to assemble the driven gear and its thrust bearing in a separate assembly which is provided with its own housing. This gear assembly is then mounted in the overall transmission casing. However, the bearing preload of this type of arrangement must be adjusted when the bearing and housing are assembled to the second gear and a threaded fastener such as a nut is normally used for this purpose. However, when mounting the assemblage, the gear position must be adjusted upon assembly using shims and another fastening nut. Therefore, such constructions are quite complicated.
It is, therefore, a principal object of this invention to provide an improved driving arrangement for driving a shaft including a bevel gear and thrust bearing.
It is a further object of this invention to provide an improved structure for assembling a driven gear and supporting thrust bearing within a housing.
One typical application in which bevel gear drives of the type described are employed is in the outboard drive unit of a marine watercraft. Such outboard drive units, and particularly the outboard drive portion of an inboard-outboard drive, employ a bevel gear arrangement for driving the drive shaft from the input shaft of the outboard drive unit. The input shaft is driven by an engine that is mounted internally of the hull of the associated watercraft. Recently, there has been a demand for the use of twin outboard drives wherein two such outboard drive units are mounted on a given hull. With such an arrangement, it is desirable to insure that the propellers associated with the outboard drives rotate in opposite directions so as to achieve balancing of the driving thrust, one of the principal reasons why such twin drives are employed. The construction can be simplified if the same general overall construction is used for each unit of the twin drive. This can be accomplished by employing an arrangement for reversing the direction of rotation of the drive shaft internally of the outboard drive. However, conventional outboard drives are designed so as to take thrust of the drive shaft in only one direction.
It is, therefore, a still further object of this invention to provide an improved driving arrangement for a marine outboard drive wherein reverse thrusts may be taken on the drive shaft through an improved thrust bearing and mounting relationship.